Blender randomly loses environment texture
I run into this issue all the time, mostly when using scenes that have DDS files as textures.  No idea what the issue is, but I use a workaround to avoid it.

If you run it from the command line with a limited number of frames per run, you can do the whole run without worrying about getting the pink textures.  For example, the following series of commands will render frames 640 through 669, in 3 batches of 10 frames each.  By using the #### format in the render output, it will automatically put the frame number into the filename.  That way you can get a nice image sequences without running into the texture issue.

blender --background intro_scene.blend --engine CYCLES --render-output //tmp/HM-####.png  -s 640 -e 649 -a
blender --background intro_scene.blend --engine CYCLES --render-output //tmp/HM-####.png  -s 650 -e 659 -a
blender --background intro_scene.blend --engine CYCLES --render-output //tmp/HM-####.png  -s 660 -e 669 -a


No idea why it does this in the first place.  It's really frustrating.  Here's the full error for anyone who wants to dig into it a bit more:

Failed loading CUDA kernel C:\Program Files\Blender Foundation\Blender\2.79\scripts\addons\cycles\lib/filter_sm_52.cubin.
Error: CUDA error at cuModuleLoad: File not found